Hydration for Active Individuals & Athletes

Your Hydration Guide

We all know that water is the fluid of life. We've been told that it's important for our overall health - but why?

Knowing a little bit about the science behind nutrition recommendations can help to maintain discipline in hitting them more consistently.

Here are some reasons we need to hydrate adequately:

• Water accounts for approximately 60% of total body weight in a normal adult. Despite such a large amount, just 1% loss of body water influences symptoms of dehydration.
  

• Water is the medium for blood transport and is required to maintain blood volume. Habitual low water intake has been associated with poor cardiovascular (heart) health, and is thought to be caused by blood vessel function and blood pressure control.
  

• Water is the medium where nutrients are dissolved and transported, and chemical reactions in our cells can occur. Without optimal nutrient transport, we can expect physical and cognitive function would be limited.
  

• Water is crucial for body temperature regulation (thermoregulation). It absorbs and distributes heat generated from digestion and muscle contraction. During exercise, body water is lost though sweat and the breath. Even if you're not a big sweater, you're losing water.
  

• Water makes up the majority of the fluid in our joints. Often overlooked, sub optimal hydration could impact joint health.

Roles of Water during Training and Sport

Effects of Dehydration on training and sport.

Dehydration is measured as a percentage. 1% of dehydration equals 1% percent of body weight from body water.

• 1% of dehydration can impact the amount of blood pumped from the heart (stroke volume) by 10%. With less blood pumped per beat, the heart has to work harder to keep up the demand from exercise, and the muscles may not receive oxygen as efficiently.
  

• 2% dehydration can increase the perception of exercise difficulty (perceived exertion) significantly. If you're thinking your workout is particularly hard today, consider how much water you've drank in the past 48hours.
  

• 2 - 4% dehydration can impact performance significantly. Strength output and aerobic capacity can plummet by up to 30% at this level of dehydration.

How much water do we need?

For the average person, the general recommended water intake is 2.1 L/day for females and 2.6 L/day for males. This does not include water in food.

Using body weight, 30ml/Kg/day is another good guide. This is 2.1L per day for a 70kg person.

And during exercise?

For people who perform exercise at high intensities (CrossFit) or long durations (endurance activity), the goal should be to consume the above recommended amount, ensuring well hydrated beforehand, with additional intake during exercise.

Needs during exercise will depend on sweat rate, temperature, intensity and duration of exercise, but as a broad rule of thumb 400-600ml per hour of exercise is recommended.

Over hydration before exercise may influence poor nutrient absorption and potentially low electrolyte to fluid balance (hyponatraemia).

A summary of recommended water intake for exercise:

Source: ACSM Position Stand on Fluid Balance

What type of fluid is needed?

In most cases the every day person just needs every day water.

If exercising for durations longer than 1 hour, a carbohydrate solution may be beneficial to maintain performance and delay fatigue. Carbohydrates are the primary fuel source for exercise, particularly at higher intensities.

Despite lower intensity exercise (up to 60% Vo2max) using a substantial amount of fat for fuel, carbohydrate stores in the body are still used and depleted by longer form exercise.

During continuous moderate to high intensity exercise or sport, lasting longer than an hour, 30 to 60g of carbohydrates should be consumed.

Hypotonic Fluids

These are drinks with a lower concentration of glucose than in the blood (hypo = under). They'll likely not be beneficial for performance, whereby water may be the cheaper and more effective fluid of choice.

Isotonic Fluids

These are the common sports drinks on the market, usually containing the same sugar concentration as the blood (Iso = same). On average these fluids will provide about 30g of carbohydrate per 500ml bottle.

Some people may get some stomach upset from these drinks, so test them out in training, and sip at regular intervals, rather than guzzle in one shot.

Hypertonic Fluids

These have glucose concentrations greater than that in the bloodstream (hyper = high). It can cause water to get pulled into the gut to dilute it, thus not helping with hydration, and causing stomach upset. This would really only be reserved for high intensity activity of longer durations, and should be tested out by the individual.

Do we worry about electrolytes?

Electrolytes sodium and potassium influence fluid regulation in the body heavily. They also is play a key role in muscle contraction of heart and skeletal muscle.

During exercise electrolytes are lost through sweat, however these are usually replaced very easily within 24 hours through a normal diet. Therefore, within-exercise replacement wouldn't be necessary.

If exercising in environments that induce excess sweating (high heat and/or intensity), or food intake has been compromised before this type of exercise bout, an electrolyte drink may be beneficial.

For the everyday gym goer, just focus on regular adequate water intake.

Monitoring your hydration

There are some lab tests available to assess hydration status, but we'll leave this to the scientists.

Us every day folk can simply monitor the frequency and colour of our urine.

Everyone goes to the toilet at different frequencies, but - believe it or not - some researchers put it to the test. Less than six pees over 24 hours correlated to higher thirst and likelihood of being under-hydrated.

As for urine colour, the scale below shows that a straw yellow colour is what we're hoping to achieve.

In summary, drink plenty of water. Cognitive and physical performance, and mood regulation will be optimised, and as a result you'll be more likely to achieve your weight loss or physique goals.

If energy levels and mood are optimised you'll likely make better food choices, and be more inclined to remain consistent with training. If nutrient absorption is optimised you'll not only be in better health, but can train harder, recover better, and progress further.